1. Field of the Invention
The present invention relates to a buckle applied to various kinds of fastening belts such as a suspending belt for bags, a human body restraining belt and the like, and more particularly to a buckle having a feature in a mounting portion of the belt.
2. Description of the Related Art
Conventionally, a buckle connecting between belts and an effective belt length can be adjusted is constituted by a plug and a socket as disclosed in, for example, Japanese Patent Laid-Open Publication No. 63-160605 and Japanese Utility Model Laid-Open Publication No. 7-24105, and is structured such that engaging portions are formed at tip end portions of a pair of insertion leg portions linearly projecting from a base portion of the plug and engaged portions with which the engaging portions are to be engaged are provided in the socket. Further, both side surfaces of the pair of the insertion leg portions have operating portions for canceling engagements of the engaging portions engaged with the engaged portions within the socket, and have opening portions through which the operating portions expose in an engaging state of the plug and the socket.
An operation of the buckle is performed by inserting the plug in the socket from an insertion port thereof and engaging the engaging portions of the insertion leg portions with the engaged portions within the socket while elastically deforming. At this time, the pair of insertion leg portions abut against the engaged portions within the socket at the side surfaces according to the inserting operation, and the insertion leg portions are elastically deformed inwardly toward each other and return, so that the engaging portion and the engaged portions are engaged with each other. Further, when the buckle is released, the engagement is released by pushing the operation portions of the plug exposed from the opening portions of the socket inwardly so as to elastically deform the insertion leg portions, so that the plug is pulled out from the socket.
On the other hand, in addition to the buckle provided in end portions of a pair of belts, as disclosed in U.S. Pat. No. 4,457,052 and Japanese Patent Laid-Open Publication No. 8-140712, for example, there is a buckle constituted by two sets of plugs and a socket to which the two sets of plugs are inserted so as to be engaged therewith, in which each of the plugs has an insertion portion projecting from a base portion thereof and the socket has a pair of portions to be engaged with and released from the respective engaging portions of the insertion portion. For example, in accordance with the buckle disclosed in Japanese Patent Laid-Open Publication No. 8-140712, the insertion portion is constituted by a plate body having engaging hooks at its tip end, a base end of each engaged portion is supported at an end of an insertion port on a back surface side of the socket, an end thereof is bent so as to be formed as a push button exposing from a central opening portion at a front surface side of the socket and capable of being elastically deformed, and hooks which are engaged with the engaging hooks of the plug are provided. When releasing the engaging hooks in an engaged state from the engaged hook, they can be easily released by pressing the push button exposing to the surface of the buckle.
Here, in the buckle mentioned above, with respect to the belt mounting portion in the plug in which the effective length of the belt can be adjusted, the belt mounting portion in each of the plugs disclosed in the Japanese Patent Laid-Open Publication No. 8-140712, for example, extends in an inclined manner toward a back surface side of the socket with respect to an outwardly extending direction of the belt. Then, a rectangular belt mounting hole to which a tip end portion of the belt is inserted and a turn-up rod provided in the belt mounting hole so as to reciprocate in the belt extending direction within a predetermined range and rotate around axial portions at both ends within a predetermined angular range are provided in each of the belt mounting portions.
The turn-up rod is structured such that the axial portions at the both ends are loosely fitted to elongated holes formed through walls on right and left side of the mounting hole. The axial portions at the both ends of the turn-up rod have a width at which they can reciprocate in a belt extending direction within the elongated hole at a predetermined distance, and is formed in an oval cross section with which they can rotate at a predetermined angle. Further, uneven portions eating into the belt are projected from edge portions of front and rear ends in the belt extending direction of the mounting hole so as to be opposed to the turn-up rod. The same uneven portions are formed on end surfaces of the turn-up rod mutually opposing to the former uneven portions. Further, a cross-sectional configuration of a main body of the turn-up rod is formed in a diamond shape having two lines parallel to a direction of a long diameter of the axial portion, and is structured such that when the main body of the turn-up rod rotates within the mounting hole, acute angle portions are brought into contact with front and rear inner wall surfaces of the mounting hole in the belt extending direction with the belt held therebetween.
When pulling the belt inserted to the mounting hole and wound around the turn-up rod in a longitudinal direction of the buckle, the main body of the turn-up rod moves in the belt extending direction within the elongated hole. At this time, a rotation moment acts on the turn-up rod, the acute angle portions strongly press the inner wall surface of the mounting hole by nipping the belt, and the uneven portions of the both elements press the belt therebetween in the front and rear portions so as to securely hold the belt.
Accordingly, in order to take out the belt or adjust an effective length of the belt, when pulling the belt to a direction of the back surface side of the belt mounting portion rather than the extending direction thereof, the turn-up rod rotates in a direction of moving apart from the uneven portions around the axial portion and gaps between the uneven portions in the mounting-hole and those of the turn-up rod are increased, so that the belt is easily moved and the belt can be taken out or the effective length thereof can be adjusted. However, since the turn-up rod has narrow gaps between the turn-up rod and the inner wall surfaces of the mounting hole, a frictional force is easily generated between the turn-up rod and the belt, between two belts and between the belt and the inner walls, respectively, as usual, although the frictional force is different in accordance with a material and a structure of the belt. Accordingly, when taking out the belt or adjusting the effective length of the belt, the turn-up portion of the belt can not easily move, so that an operability is far from excellent. Further, there is a case that the turn-up rod accidentally rotates when using the buckle, and there is a problem that the belt is loosened and moved at this time, so that the belt can not be maintained at a predetermined adjusted length.